Influence of spray angle in cold spray deposition of Ti-6Al-4V coatings on Al6061-T6 substrates

Abstract

Cold spray (CS) has been deployed to deposit compact and well bonded Ti-6Al-4 V (Ti64) coatings. While the effects of gas pressure, gas temperature and powder feed rate have been well studied, the influence of spray angle during CS deposition of Ti64 powders is less understood. As actual components frequently have uneven or curved surfaces, it is critical to understand the impact of spray angle to design an efficient toolpath for repair or additive manufacturing of 3D freeform objects. In this work, off-normal spray angles were studied to elucidate their impact on the coating quality when depositing spherical Ti64 powders by CS on Al6061-T6 substrates using nitrogen as process gas. Evaluation of deposition efficiency and the coatings' surface roughness, cross-sectional microstructure, thickness and residual stress were performed to provide insight on the effects of spray angle. Finite Element Method (FEM) simulations were also performed in order to understand the dominant Ti64 deformation mode and development of residual stress in the coatings. Spray angle is identified to be an effective process parameter to control porosity, pore alignment and extent of surface compressive residual stress in the CS deposited materials. • Ti-6Al-4V powders were cold-sprayed onto Al6061-T6 substrates at 50, 60, 70 & 90°. • Decreasing spray angle led to increasing porosity & decreasing residual stress in Ti64. • Spray angle greater than 70° led to dense coating with low porosity • FEM simulation shows shear deformation induced compressive residual stress in Ti64. • Spray angle is an effective parameter to control cold-sprayed deposits' properties.